DHEA can be measured anytime during the day. Cortisol, on the other hand, is the highest in the morning (helping to wake up) and lowest in the evening before bedtime (helping to fall asleep). Taking 4 samples of cortisol (at 8 am, noon, 5 pm, and before bedtime) is the most accurate. With multiple samples taken throughout the day, we are able to map the daily diurnal curve (circadian rhythm) of free cortisol in the body. This will give us a much clearer picture of adrenal function. Inversion of the rhythm, increased peak values at bedtime and decreased peak values in the morning, may explain difficulties falling asleep, waking up tired, and fatigue throughout the day. A total cortisol (not free) measured in the blood at 8 am is inaccurate and inappropriate (and who gets it tested at night?). Remember that high level of morning cortisol provides the energy needed for the day, and cortisol is necessary for thyroid to get into the cells to work.
Interesting that we can get commonly measurements of T4 free and T3 free in blood test but not free cortisol – serum free cortisol levels are only available at some hospital laboratories, or upon request of endocrinologists.
Saliva testing advantages
When compared with serum testing, saliva testing offers several advantages. Saliva collection is simple, at home, noninvasive, stress free, painless. The transport via the post of saliva samples for assessment is inexpensive. Hormones are stable in saliva for three weeks at room temperature.
In addition of checking adrenal disorders, saliva testing provides an accurate assessment for other free steroid hormone levels, and can be used to identify a number of clinical conditions, including climacteric changes in pre-menopausal, menopausal or post-menopausal women, estrogen dominance, with free estrogens levels (estradiol, estrone, estriol), and free progesterone levels; for men, to explore androgen deficiency (free testosterone, free 5 alpha-dehydrotestosterone, free androstenedione). All are steroid hormones, a class of body substances that derive their name from the fact that they are built upon the structure of the common cholesterol molecule.
In conclusion, as shown in both clinical practice and published studies, saliva testing provides an accurate measurement of steroid hormones and offers advantages not provided by serum testing.